Decorated square-kagome quantum antiferromagnets provide a natural setting in which strong frustration, lattice decoration, and spin-orbit-induced anisotropy compete on comparable energy scales. Here we show, within a Schwinger-boson mean-field treatment of the realistic Hamiltonian, that the coupling $J_{10}$ linking the decorating Cu(3) sites to the square-kagome backbone stabilizes the gapped saddle point, while symmetry-allowed Dzyaloshinskii-Moriya (DM) interactions systematically suppress the minimum spinon gap ${\mathrm{\Delta }}_{\mathrm{spinon}}$ and enhance the tendency toward boson softening. To establish this, we combine ab initio calculation of the DM vectors with a Schwinger-boson self-consistent mean-field treatment (SBMFT) extended to include the triplet hopping and pairing channels required by explicit spin-rotation-symmetry breaking. As a benchmark, the isotropic square-kagome Heisenberg model exhibits four competing low-energy saddle points distinguished by their Wilson-loop fluxes and by characteristic static and dynamical structure-factor fingerprints. A minimal DM perturbation does not qualitatively reshape this competing landscape, but already enhances low-energy spectral weight in the ordered saddle points. For the realistic decorated Hamiltonian, finite-size scaling of ${\mathrm{\Delta }}_{\mathrm{spinon}}$ together with momentum-resolved structure factors identifies $J_{10}$ as a control parameter for the stability of the gapped mean-field regime and shows that the full symmetry-allowed DM pattern shifts the spectrum toward lower energies. Our results indicate that, within SBMFT, ${\mathrm{Na}}_6{\mathrm{Cu}}_7{\mathrm{BiO}}_4{\left({\mathrm{PO}}_4\right)}_4{\mathrm{Cl}}_3$ lies close to a regime where the gapped saddle point becomes soft, and provide experimentally testable predictions for anisotropy-enhanced low-energy spectral weight in decorated square-kagome materials.

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• Dzyaloshinskii-Moriya interaction
• Frustrated magnetism
• Magnetic anisotropy
• Transport in heavy-ion collisions
• Antiferromagnets
• Quantum spin models
• Schwinger boson method